How many of you guys trim all your once fired 223 brass. I have heard some say to trim it after it is once fired and then you won't have to trim again because the cases will wear, split the neck etc before they need trimmed again. Is this true or not ?
How do you guys determine when to trim your brass ?

trimming once fired 223 for AR ?
How many of you guys trim all your once fired 223 brass. I have heard some say to trim it after it is once fired and then you won't have to trim again because the cases will wear, split the neck etc before they need trimmed again. Is this true or not ?How do you guys determine when to trim your brass ?

By measuring.

As for the trim once, they'll not need trimming, not always. IF you closely control how much they stretch with each firing, THEN you might get away without trimming every time. By that I mean, setting the shoulder back the minimum that will allow full chambering and positive lock-up.

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I trim all my rifle brass at each reload, every time, run it threw the motions whether it needs it or not. I have it in my head that it’s a part of consistency, and consistency is a key to accuracy. Strange part about it, I trim pistol brass once and forget it.

Most folks who want to trim only once will trim the brass back to its minimum spec on the first trim or sometimes even a bit shorter. SAAMI has lengthened this for the .223 Rem in 2001, and the minimum spec is now 1.730 in¹. If you trim to that number instead of the usual 1.750 in, you'll get longer time between trims. Just keep in mind this strategy is not for folks who crimp their loads, as it not only requires a change in the crimp setting, but also because the cases don't tend to grow completely uniformly (some more than others at each firing). You do best to trim each time if you crimp.

Pistol brass seldom needs it unless you shoot the very high pressure uber magnums. The reason is that brass doesn't typically stick to the chamber and start stretching until you get somewhere up above the 30,000 psi load range. Below that, the whole case just backs up in the chamber. That can widen and fatten the cases so the brass flows back on resizing, with the result the cases actually shrink. I once ran some .45 Auto case through 50 load cycles with light target loads and found they lost an average of half a thousandth per load cycle, landing about 0.025" short at the end.

¹ The spec is actually 1.760 in, -0.030 in. It used to have a tolerance of -0.020 in. The military has a still tighter minimum, with a tolerance of -0.015". But the military only fires their cases once, so they don't need to worry about growth.

A quick and easy way to measure and trim your cases, if used for general purpose shooting, is by use of Lee's trimmers. They will trim your cases to "Lee length" which is fine for most purposes outside match or long range varmint shooting. People refer to "LEE length" because in using this system you do not know just exactly where you have trimmed the case length unless you have calipers or other case measuring tools. Generally, those folks with calipers and etc. also have Wilson or Forster or other lathe type case trimmers. In addition, you may end up with cases which were too short for "LEE length"trimming, while most folks using the lathes will trim all the cases to equal the shortest one (within reason) in the bunch.

I have the Lee trimmers and I have a lathe trimmer and I use both. I can say that it has been my experience that the Lee trimmers work just fine when used on cases meant to shoot a deer in the brisket with a .30-30 or a .30-o6 or to bang the 200 yard 8" gong with my AR. Lee length may not work so well in my 6mmBR or 30BR which I require to shoot a lot tighter groups. Trimming to exact length for my AR does not seem to be an activity that results in any improved accuracy for me and is therefore a waste of my time. The same activity when used to produce cases for my .223 varmint rifle does seem to be worthwhile, resulting in tighter groups at 200 yards or more. I actually did do a side by side comparison of the two methods some years ago.

This might be a dumb question, but I am new to rifle reloading. Will be loading once fired .223 brass on a Dillon XL650. I am going to buy their electric case trimmer die set up.

Do you have to re-size before trimming, or can you trim, then re-size. i guess that is such a dumb question I probably already even know the answer, but the reason I ask if I am trying to figure out if I can put the trimmer die on an RCBS single-stage press and just trim all the brass, then run it through the dillon for re-size and de-prime, re-prime, load with powder, seat bullet, crimp (do I need to crimp??? Lyman 49 says rounds for AR's need crimping; are they right?). Otherwise, if I have to re-size first, then trim, I am not sure where the trimmer die goes. It can't go into the die position in the tool head that is used for the powder measure for the pistol rounds, right? So confusing.

You always have to full length resize before trimming because it's in the sizer die that they grow. I always trim my once fired 223 brass before loading it. Then I de-burr the flash holes. This system works well for me.

The WFT is very accurate and extremely convenient. Trimming brass sucks, the WFT makes it suck less

and each case takes 3 sec max. you can tell right when you put it in there if it needs trimming or not. for me plinkers if it doesn't make contact with the bit i toss it right in the done pile. for the ones the need trimming i leave it in there for the other 2 seconds

for me accuracy rounds i separate by headstamp, measure the shortest and trim to that length by hand with the lee trimmer (yes you can).

Last edited by the led farmer; October 12, 2012 at 12:03 AM.
Reason: added info

very accurate !!, i just bought one several weeks ago for the .223 Rem., trimmed over 1,000 G.I. cases to 1.740", i mounted mine on a 1,400 RPM motor with a 1/2" chuck on the motor shaft. the inside of the trimmer is a "live" bearing with the dimensions of the case shoulder after sizing, when you insert a case to be trimmed use a gradual pressure on the case then increase pressure till done, the case holder will stop spinning due to hand pressure against the shoulder.., one word of caution, wear a glove on your hand or you will get a blister on your thumb and index finger.., i know this from experience, i now have a very sore thumb and finger....., my trigger finger !!

Will be loading once fired .223 brass on a Dillon XL650. I am going to buy their electric case trimmer die set up.

Do you have to re-size before trimming, or can you trim, then re-size.

The general answer is to size before trimming, since sizing (full length sizing in particular) causes the case to lengthen. However, in the specific case of the Dillon RT1200B trimmer you have a Full Length die and a trimmer combined, so it will inherently size before trimming and there's not much you can do to change that (apart from enlarging the dimensions of the die). Some choose to run a body die before the Dillon trimmer, some run a Small Base die after it, and there are probably other combinations in use too, but you'd probably want to try the RT1200B on its own first and only look at additional complications (and increased working of the brass) if you have problems. Bear in mind that the die in the RT1200B does need to grip the case, so excessively sizing the whole case before the RT1200B is probably not a good idea. Note also that the neck dimension of the RT1200B die is quite tight compared to what you might choose for match ammo in some calibers.

toss that "5 times" brass my way.., i have recorded well over 15 reloads on one lot of GI brass, that particular lot of brass (500 cases) has been trimmed twice and there is no sign of wearing out, this lot of brass is my personal test of how many reloads per case with GI brass.

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